A 35-year-old woman is admitted 4 hours after a tibia fracture sustained in a fall from height. She reports severe leg pain and tightness in the anterior aspect of the leg. On examination, the leg is markedly swollen and tense. Passive dorsiflexion of the foot elicits severe pain. Foot pulses are palpable and sensation is intact. Intracompartmental pressure measurement shows 35 mmHg in the anterior compartment (diastolic BP = 70 mmHg). What is the most likely consequence if fasciotomy is delayed by 8 more hours?

Explanation

## Pathophysiology of Delayed Fasciotomy in Compartment Syndrome **Key Point:** Muscle tissue is exquisitely sensitive to ischemia. Irreversible damage begins within 6–8 hours of compartment syndrome onset. Delay beyond this window results in permanent contracture, weakness, and loss of function — even if limb salvage is achieved. ### Timeline of Ischemic Injury in Muscle | Time Since Onset | Pathologic Changes | Clinical Consequence | |---|---|---| | 0–2 hours | Edema, increased pressure | Reversible if decompressed | | 2–6 hours | Early myonecrosis, enzyme release | Mostly reversible with urgent fasciotomy | | 6–8 hours | Extensive myonecrosis, rhabdomyolysis | Partial recovery; some permanent damage | | 8–12 hours | Severe, widespread muscle death | Volkmann's contracture, permanent weakness | | >12 hours | Complete muscle necrosis, fibrosis | Severe contracture, amputation often necessary | **High-Yield:** The critical window for fasciotomy is **within 6–8 hours** of symptom onset. This patient is already 4 hours in; delaying 8 more hours (total 12 hours) puts her well beyond the point of reversibility. ### Understanding Volkmann's Contracture **Definition:** Volkmann's contracture (or Volkmann's ischemic contracture) is a permanent flexion deformity and weakness of the forearm and hand (or leg, in this case) caused by ischemic necrosis and fibrosis of muscle following compartment syndrome or vascular injury. **Mechanism:** 1. Compartment syndrome → sustained ischemia of muscle 2. Myonecrosis → muscle fiber death 3. Replacement by fibrous scar tissue 4. Scar tissue contracts → fixed flexion deformity 5. Loss of strength in affected muscle groups **Clinical Presentation in Anterior Compartment Syndrome:** - Loss of dorsiflexion strength (foot drop) - Fixed plantarflexion deformity - Clawing of toes - Sensory loss in first web space (deep peroneal nerve territory) - Permanent disability despite limb salvage **Clinical Pearl:** Volkmann's contracture is a **preventable complication** if fasciotomy is performed urgently. Once established (after 8–12 hours of ischemia), it is largely irreversible and requires reconstructive surgery (muscle transfer, tendon transfer) with limited functional recovery. ### Why This Patient's Pressure Mandates Immediate Fasciotomy **Intracompartmental pressure = 35 mmHg** **Diastolic BP = 70 mmHg** **Delta P = 70 − 35 = 35 mmHg** **Fasciotomy threshold:** Pressure ≥30 mmHg OR delta P ≤30 mmHg → **URGENT fasciotomy** This patient meets the threshold (pressure 35 mmHg; delta P 35 mmHg is borderline but with high clinical suspicion, fasciotomy is indicated). The 4-hour delay already puts her at risk; further delay guarantees irreversible damage. ### Rhabdomyolysis and Acute Kidney Injury Massive muscle necrosis releases: - Myoglobin → myoglobinuria (dark urine) - Potassium → hyperkalemia (risk of cardiac arrhythmia) - Phosphate, uric acid → hyperphosphatemia, hyperuricemia - Creatine kinase (CK) → markedly elevated **Management:** - Aggressive IV hydration (target urine output 200–300 mL/h) - Alkalinization of urine (sodium bicarbonate) to prevent myoglobin precipitation in renal tubules - Monitor electrolytes, CK, creatinine, urine myoglobin - Dialysis if acute kidney injury develops ### Why Other Options Are Wrong ```mermaid flowchart TD A[Compartment syndrome<br/>4 hours post-injury]:::outcome --> B{Fasciotomy within 6–8 hours?}:::decision B -->|Yes| C[Complete or near-complete recovery]:::action B -->|No: delay 8+ more hours| D[Irreversible myonecrosis]:::urgent D --> E[Volkmann's contracture<br/>permanent weakness<br/>fixed deformity]:::urgent E --> F[Reconstructive surgery<br/>limited functional recovery]:::action ``` **Option 0 (Transient paresthesias, complete resolution):** Transient paresthesias occur with mild, brief nerve compression and resolve fully within days to weeks. In compartment syndrome with 12+ hours of ischemia, nerve damage is often permanent due to axonal degeneration. Even if paresthesias resolve, motor loss (weakness, contracture) persists. **Option 2 (Acute arterial thrombosis, amputation):** While compartment syndrome can eventually compromise vascular flow, the patient has palpable pulses at 4 hours, indicating patent vessels. Arterial thrombosis is not the primary mechanism of tissue damage in compartment syndrome; ischemia from elevated interstitial pressure is. Amputation is a late consequence of uncontrolled rhabdomyolysis and sepsis, not the direct result of 12-hour delay in fasciotomy. **Option 3 (Spontaneous resolution):** Compartment syndrome does NOT spontaneously resolve. Swelling may eventually decrease, but by that time, muscle is already necrotic. The pressure remains elevated until fasciotomy decompresses the compartment. Waiting for swelling to subside is catastrophic. [cite:Campbell's Operative Orthopaedics 13e Ch 48; Rockwood & Green's Fractures in Adults 9e Ch 1; Harrison 21e Ch 295]